Process of maintaining the vitality of dried yeast.



UNITED STATES PATENT OFFICE.

PETER DIEDRICII HINRICI-I'QHLHAVER, SANDE, GERMANY.

rnoonss or MAINTAINING THE VI'IALITY or DRIED YEAST. j

N Drawing.

To all whom may concern.

Be it known that I, PETER DIEDRIGH.

HINRIGH Orinmwnm'a subjectof the Emperor of Germany, residing at Sande, Germany, have invented certain new and useful Improvements in Processes "of Maintaining the Vitalitymf Dried Yeast, of. which the following .is a specification.-

This invention relates to a process of treating dried yeast, and has for its object to maintain the vitality of its active organisms and render them eifective after any lapse of time, and under severe climatic variations. v

When it is desired to prepare .fresh yeast for use after long periods of time, and. par ticula-rly for shi ment to tropical climates,-

it has been usua to subject it to a drying process which can safely be done without killing the yeast if -certain precautions are taken. To facilitate the drying-ofthe yeast, the fresh yeast is frequently mixed with various water absorbing substances during the drying "process, and for the better preservation of the dried product it is kept in air tight receptacles. In spite of these pre cautions however the life of the. dried yeast as hitherto madegradually ebbs away, the

destruction being much accelerated when the yeast is exposed to high temperatures;

, This circumstance has led to it being known that the supposed preservation of yeast has been quite an illusion hitherto, and no rem-' edy has been found because the cause of the decay could not be ascertained. By careful experiment extending over a number of.

. years I have four-id out the causes of the decay of the dried yeast and have also at the same. time invented a process which will keep the dried yeast permanently alive even inhigh temperatures.

Dried yeast is hygroscopicand obstinately retains even when exhaustively dried a certain amount of humidity; This small amount of humidity in itself does not harm. the dried yeast. However the dry yeast, in

spite of its hygroscopic nature, gradually I gives'up,'especially in higher temperatures,

a part of its humidity to the air still existing in' the air tight receptacle in which it is packed, and it is just this vaporous humidity which proves itself so ruinous to the life ."of the dry yeast. WVhen the vaporous -hu'- midity is present, the enzymes 2'. e. the active constituents of the yeast are awakened from their dormant state,-and become excited and Specification of- Letters Patent.

Application filed August 24, 1911. Serial lid-645,830.

Patented Oct. 1, 1912.

active. For Want" of suitable work these constituents finally destroy themselvesand the dry yeastdies away. v

In order to maintain the enzymes of dry yeast in "a state of repose, the existence of vaporous humidity in the yeast receptacle 1) 11st be'prevented, or better'still the air in the receptacle must be kept permanently dry. This essential I obtain by inclosing in the-air tight receptacle along with the 'dry yeast a hygroscopid substance in such a manner that the dry. yeast and this hygroscopic substance are separated from .each other. For instance within the airtight 'receptacle the dry yeast can be placed on one side and the hygroscopic substance on the other side; or the dry. yeast and the hygroscopic substance are separated in the air tight receptacle by meansof a suitable partition which however must allow of the air passing throughit; such a .partition may be made of perforated tin, linen. gauze, and

the like. It is essential that the dry yeast and the hygroscopic substance do not mix .-but remain, separated and that in the case of a partition, thelatter be'so constructed as to letfthe air pass through in order that the hygroscopic substance may permanently keep the air dry in the yeast portion of the receptacle. When the dry yeast .gives up its final humidity to the surrounding air, the vaporous humidity which would otherwise arise is at once, absorbed-by the hygroslcopic substance, and the air is thus kept ry. use preferably starch, or substances contain- For such. a hygroscopic substance I ing starch, chlorid of calcium, and chlorid of magnesium. These substances have not only the property of\ quickly. absorbing vaporized water, thus drying-the air, but they ceptacle, could never be attained in that way. In my' process the yeast is first dried withno admixture of starch, but when the starch is subsequently added in the yeast receptacle'it is kept separated from the yeast.

It is also known that fresh yeast hasgbeen wrapped-in blotting paper with which it is dried the parcel thus formed-'-dry to a certain degreebein'g afterward enveloped in a layer of burnt gypsum and closed up airtight. By enveloping the freshyeast with blotting paper it is sought to avoid infection of the yast during thedrying process,

and the further envelopment -with burnt gypsum is for the purpose of obtaining an increased drying effect. The blotting paper absorbs the water in the yeast and the gypsum absorbs the water from the blotting paper. These and similar materials absorb the water mechanically when in direct contact with each other, but they are quite use- ,less for my process because they are not hygrosoopic, that is to say they'do not absorb vaporized-humiditycontained in the air and are therefore not capable of drying-theair in the yeast receptacle andkeepin'g'it in a dry condition. y p

With my process I have kept dry yeast in a hot chamber at a temperature of 40 to 45 degrees C. for 7% months which as regards its active characteristics has remained per-- fectly effective up \to date. The same dry yeast also in airtight receptacles but with out the addition of the separatel inclosed hygroscopic. substance, had un er. equal condition after two week'slos't about 7 0% of its activity. So long as the air is -perfectly dry the enzymes of the yeast remain in their state of repose and can consequently stand high temperature without injury, and the dried yeast to the air within such receptacle. r

2. The herein described process of maintaining the vitality of'dried yeast; which consists in maintaining the thoroughly dried yeast and a hygroscopic substance containing starch out of contact within an air-tight receptacle forr'embving the hygroscopicallyretained moisture gradually given up by the thoroughly dried yeast to the air withinsuch receptacle.

In testlmony whereof I afiix my signature in presence of two witnesses.

PETER DIEDRICH HINRIGH (llILHAV ER.

Witnesses: ERNEST H L. MUMMENHorr, IDA CHRIST. HAFERMANN. 

